This invention relates to a water cooled engine and more particularly to an improved fuel supply for the charge forming system of an engine that is water cooled.
Many forms of engine charge forming systems employ one or more fuel pumps which are driven mechanically from the engine and which pressurize the fuel that is supplied to the engine. When the fuel pump is driven by the engine, heat is transferred from the engine through at least the pumping element to the fuel and can cause elevations in its temperature. This is true even though the mounting for the fuel pump on the engine is thermally insulated. When the fuel becomes heated, it tends to vaporize and cause a loss in the efficiency of the pump and a leaning of the supply of fuel to the engine.
This condition can be understood in part by reference to FIG. 1 which is a curve showing the fuel temperature, the pump pressure and the area where vapor will be generated in the fuel. As may be seen, as the temperature of the fuel increases there is a likelihood that fuel vapor will be generated by thus decreasing the efficiency of not only the fuel pumping system but the charge forming system for the engine.
It is, therefore, a principle object of this invention to provide an improved arrangement for pumping fuel for an engine.
It is a further object of this invention to provide an engine fuel pumping system wherein the fuel will not be heated excessively, even though the pump is driven directly by the engine.
It is a still further object of this invention to provide a number of different ways in which the fuel pumped by an engine can be protected from overheating.